erith



C. ERITH.

MECHANICAL STOKER.

'APPLICATION FILED 00112.1920.

Patented Oct. 10,1922.

eli- C. ER ITH.

MECHANICAL STOKER. APPLICATION FILED 0c; 12,1920.

Patented w. 10,1922.

C. ERITH.

MECHANICAL STOKER.

APPLICATION-FILED 00112, 1920. 1,431,882; Patented Oct. 10, 1922.

4 SHEETS-SHEET 3.

0. ERITH.

MECHANICAL STOKER.

APPLICATION FILED 00? I2, I920.

Patented Oct. 10, 1922.

4 SHEETS-S HEET 4.

4 when desired.

Oct. 10, 1922.

UNITED STATES PATENT OFFICE.

CHARLES ERITH, 01? SUTTON, ENGLAND, ASSIGNOR TO ERITHS ENGINEERING COMPANY, LIMITED, OF LONDON, ENGLAND.

MECHANICAL STOKER Application filed October 12, 1920. Serial No. 416,474.

siding at ll inchfield, Albion Road, Sutton,

in the county of Surrey, England, have invented certain new and useful Improvements in or Relating to lilechanical Stoker's, of

' which the following is a specification.

This invention relates to underfeed mechanical stokers for boiler and other furnaces of the kind in which the fuel is fed into troughs or retorts provided with tuyeres for the admission of forced draught air into the fuel as it rises from the retorts and spreads over the tops of the tuyeres, and in which overfeed or extension grates (hereinafter termed extension grates) are provided at the rear ends of the retorts on which the final of combustion are completed.

In underfeed stokers of this kind, the fuel is usually fed by plungers or rams into the troughs or retorts, and the fuel is usually advanced by means of variable-stroke pushers within the retorts, viz, under the thickest part of the fuel bed of each retortunit.

According to one feature of the present invention an intermediate stage is introduced into the combustion process by placing at the outer sides of the tuyiwres longi tudinal overfeed grate bars through which a supplementary supply of air under control and preferably at reduced pressure, is delivered into the partly burnt fuel, so that the fuel, after rising from the underl'eed retorts and becoming ignited as it spreads over the tuyeres which admit full pressure air into the thick part of the fuel bed above each retort, may be suopliod with :ulditional air through the longitiiidinal overfeed grate bars on which the thinner parts of the fuel bed are supported, thereby burning out the combustible matter from the partly-burnt fuel to a greater degree than heretofore. before it reaches the transverse portion of the extension grates on which the final stages of combustion are completed. The said longitudinal overfeed grate bars are preferably box-shaped and stepped and may be adapted to be reciprocated so as to slice the thinner portions of the fuel bed as and The air admitted to the fuel bed through said longitudinal overlieed grate bars is preferably ailu'iitted thereto from the secondary air chamber which supplies air for supplementary combustion to the movable transverse extension grates.

A further feature of the present invention consists in imparting positive and controlled slicing actions to the various parts of the fuel bed, well as positive rear ward travel of the fuel and ash under all conditions of combustion by independent actuation and adjustablestroke motion (1) of the pusher in each underfeed retort, (2) of the novel longitudinal overfeed grate bars, and (3) or the sectional transverse extension grates.

All three variable-stroke reciprocating motions are preferably transmitted to the parts to be actuated from the fiiiel-feedingram of each underfeed retort unit, so as to harmonize with the rate of fuel-feeding provision being made for coupling or uncoupling the actuating devices at will; for instance, the longitudinal overfeed grate bars can be so coupled as to actuate the transverse extension grate sections when desired while retaining full liberty of independent variable-stroke motions to either of these parts, as in many cases experience shows that it is desirable to have little or no regi'llar motion on the longitudinal oven feed grate bars, owing to the fact that a shearing ellect on the fuel bed is assured by the action of the pusher in each retort where the fuel bed tl'iiclcest via, over the retort centres. while it is often undesirable to employ a shearing e'lleet above the tuycre centres. where the fuel bed is necessarily relatii'ely thin. and this undesirable shearing eilert on the thin parts of the fuel bed cannot be avoided in earlier forms of stoliers Where the transverse extension grates cannot be reciprocated independently of the tuyeres; further when there is no provision for mechanically displacing clinkers which tend to form on the fixed tuyeres when tires are banked, a reverberatory action of the flames under large clinhers tends to occur when active combustion is resumed. which results in a destructive etlfect on the tuyeies.

The HOv'Ql features of the present iinvention produce a very simple constructimi and arrangement of the parts of the inecl'ianisn'i. They add to the reliability of the stoker and eliminate manual labour; while they also reduce the cost of construction and upkeep,

and make it unneressar to em 1o i movin embodying one form of the invention.

Figure 2 1s a plan view, partly in section.

Figure 3 is a cross-section of the furnace, taken on line 3-3 of Figure l, the parts beyond the-section line being omitted for the sake of clearness, and showing the fuel as it rises from the retorts and spreads over the tuyeres on to the novel longitudinal overfeed grate bars.

Fig. 3* is a detail sectional view showing the 'tuyere openings.

Figure l is a side elevation of one of the novel longitudinal overfeed grate bars and of the sliding shoe which is coupled to the sectional transverse extension grate, the lugs by which it is reciprocated being shown in sectional plan view in Figure 2 and in elevation in Figure 5.

Figure 5 is a sectional elevation on the line 55 of Figure 4t showing'a pair of such.longitudinal overfeed grate bars with sliding shoes for one unit, the shoes and lowerparts of, the bars being shown in section, and the upper parts of the bars in elevation; it also shows the side bar and shoe of an adjacent retort unit.

Figures 6 and T are corresponding views to Figures 1 and 2, showing a modified form of the invention. Figures 8 and 9 are cor-- responding views to Figures 1 and 2, showing" a still further modified form of the invention. I

In the examples illustrated in these i"; ures, the stoker is assembled in each case from four similar units, but any desired number of units can be employed, accord ing to the width and capacity of the furnace;

Throughout the several figures of the drawings the same reference letters are employed to denote similar or equivalent parts.

A is the front wall and B the bridge wall of the furnace, above which, shown in Figures 1, 6 and 10, a watertube boiler is indicated, which may be of any make or size, to correspond with the stoker capacity installed The stokers shown each comprise a number of rearwardly inclined and stationary underfeed fuel retorts (1, arranged in series above the main air chamber K, fuel being 1,431,.eee

mechanically fed from the hopper B to each retort by a reciprocating plunger or ram E worked by a connecting rod F, from a crank-shaft F by any suitable gearing, and the fuel being advanced by variable stroke pushers X located within the retorts, and connected to and actuated by the ram E.

C, C are the side walls of each retort, and D, D, are the tuyeres; the latter being preferably constituted by plates with imperforate tops, arranged in step formation as shown, and admitting air at full pressure through lateral openings D, for primary underfeedcombustion of the fuel as it rises from the retort-s and spreads over the tu'yeres. The longitudinal grate bars G, G, in the examples shown are box-shaped and of stepped formation with air outlets G in the risers, and are adapted to be reciprotional overfeed extension grates H. The fuel is advanced by the variable st-roke pusher X in each retort, actuated in the form shown in Figure 1 by means of links X detachably and adjustably connected to the fuel feeding rams E. The pushers X are stepped formation as shown and are each provided with a lug X which extends through an opening X in the bottom plate X and to which one end of the link X is connected by the crosspin Y. The other end of each link X is connected to an extension X which rests on a cross pin X" and slides between a pair of lugs X attached to the ram E, said lugs X passing through a slot X in, the ram cylinder X 7 ram X the lugs X X alternately strike pins X projecting from the extension X. in additional opening X is provided in the extension X so that by removing one of the pins X and inserting it in the open ing X the travel of the pusher X can be decreased, The fuel on leaving the lower end of the retorts flows over the transverse portion of the extension grates whereon the final stage of combustion is completed, the ash and clinker being continuously and automatically discharged from the stationary ash-support bars, I, through an opening ]')referably regulated by curved plates M, M, adapted to be adjusted or actuated as and when desired. 7

All air required for combustion of the fuel is supplied under pressure from a fan J having a primary damper J into the main air chamber K located beneath the inclined underfeed retorts; the great bulk the air thus forced at full pressure through the lateral tuyere openings D across the retorts, via, into the thickest part of the fuel bed, for primary underfecd During the movement of the I combustion. A proportion of the air, controlled by a secondary air damper L, is admitted as usual into the reduced-pressure air-chamber K, from which, as aforesaid, air at reduced pressure is supplied to the overfed grates, viz, both to the longitudinal CIT grate bars G and also to the sectional extension grates H; so that low-pressure air, suitable for the intermediate and final stages of combustion, is emitted under the relatively thin parts of the fuel bed, through the grate openings Gr and H respectively.

In the two embodiments of the invention shown at Figures 1. to 9 the inclined retorts C, C, are stationary and are usually composed of three plates bolted together, but they may be solid castings, thus obviating the leakage of fine unburnt coal that ocours in retorts which have moving Walls, and in the examples shown at these figures the underfeed tuyeres D, D, are also stationary, for a similar reason, and they are preferably bolted 1n stepped rows as shown to the stationary retort-walls.

In all three embodiments of the invention above described a novel method is provided of promoting an intermediate stage of combustion of partly-burnt fuel at the outer lines of the tuyeres by using box-shaped overfeed grate-bars supplied with air at reduced pressure, and capable of being re ciprocated. After such intermediate overfeed combustion on the longitudinal gratebars at the outer sides of the tuyeres, the fuel arrives at the transverse portion of the extension grates, in a more advanced stage of combustion than hitherto; while the final stage of combustion on the transverse portion of the extension grates is effected usual with air at reduced pressure.

Any suitable form of ash-supporting bars or plates may be used in lieu of the ash support I or plate M and any suitable meansmay be employed for usting the width of the ash-discharge opening, while if desired. an ash-crushing appliance may be employed. for crushing the ash as'it is discharged.

In the embodiment of the invention shown at liigures l, to 5 both the side walls (l, C, of each retort and also the tuyeres D, D, (as aforesaid) are stationary and the grate-bars G are adapted to be reciprocatcd longitudinally in pairs on shoes H having stepped sides H on which the plates ii, constituting the extension grates H. are mounted, the requisite reciprocating movement being imparted thereto by means of push rods 6, 6 attached at one end to lugs c* on the grate-bars G. The ends of the links 6, e are reduced in diameter and slide freely through openings in cross bars 6, (1 attached to the fuel feeding rain ll. Mounted on the said reduced portions are nuts c*. 6 adapted to be struck alternalely by the cross bars a, e. iy adjusting the position of the nuts 6, e* on the cross bars 6, e the travel of the grate bars G, G can be made less by any desired amount than the travel of the ram E. In the embodiment of the invention shown at Figures 6, 7, 8 and 9, the grate-bars Gr, as also the extension grates H, and the pusher X are adapted to be reoiprocated by means of links 6 e and e adjustably and detachably connected to pivoted members a, which in turn are coupled to and adapted to be actuated by arms 6 from the connecting rods F and operated by the crank shaft F. Pivotally connected to the arm is one end of a lever c which carriers a number of pins 6 c on which the outer ends of the links 6 e and 6 rest, the other arm of the lever e being pivotally connected to a link 6" pivotally attached to the front plate 6 of the furnace. Each of the links 6 e and 6* carries pins 6 whichare adapted to be struck alternately by the lever 6 Additional openings 6 are provided in the links 6 e and 6 so that the position of the pins 6 can be altered and the travel of the links 6 e 6 thereby varied. The inner 'end of the link 6 is connected to a cross bar 6 on the extension grate II, and the inner end of the link a is attached to a lug on the stepped pusher X. The inner end of the link 6 is connected to a depending link 6 on the floor plate of the furnace. The links 6 e 6* are connected to their respective supports by the cross pins Y e and a, respectively, as shown. Extending transversely of the furnace is a plurality of shafts the ends of which are attached by means of links 6 to lugs 6 on the grate bars G. Owing to this arrangement and by attaching or detaching one or more links and c and 6* from the pivoted members c the grate-bars G, the pusher It. or the extension grates H can either be actuated .in unison with, or in ;le pe1nlently of each other as desired.

In the embodiment shown at Figures 10 and 11, the side walls of the retorts as also the tuyeres carried thereby are movable and are coupled with an adjustable motion to the crank-shaft F, connecting rod F, and i ram E, through the intermediary of push rods 18 coupled to cross-bars e. The gratebars are adapted, as in the arrangement shown in Figures 6, 7 and 8, to be actuated by "he connecting rods F through arms 6 and the pivoted members 6 which are op eratively associated with links 0 e 6 and c. In this embodiment of the invention a variable stroke pusher X is also shown located within each retort; but this may be dispensed with if desired. The extension grates II are mounted upon a shoe which is adapted to slide upon a fixed plate 70" and the side walls D of the retort are connected to the sliding shoe is by meansof a pin 70.

l. l O

extension grates H, with 01' Without reciprocating the longitudinal o'verfeed grate- .bars G, the partly-burnt fuel and refuse is agitated sufficiently to break up, clinkers and to separate combustible matter from the ash.

All the advantages of stationary retortwalls and stationary tuyeres are thus combined. with continuous but adjustable feed ing motions for the fuel and ash, and for positive and controlled slicing actions for the various parts of the entire fuel bed, together With the novel provision for effecting an intermediate stage of overfeed combustion at the outer sides of the tuyeres of each retort-unit. i

The reciprocation of the over-feed grate bars, as Well as of the fuel pushersand of the extension grates, assures shearing or slicing lines at all points Where clinkers tend to fornr By suitably regulating these motions, the accumulation of masses of clinker can be prevented in any part of the furnace, and thereby the destructive reverberatory action of the flames under large clinkers (such as often occurs in stolrers not provided With such means for slicingaction,) is prevented, and continuous mechanical operation is assured, irrespective of the size of the stolter and furnace.

l/Vhat I claim and desire to secure by Letters Patent of the United States is :e,

1. An under-feed mechanical stoker comprising troughs or retorts, means for feeding fuel into said troughs or retorts, tuyeres at the sides of said troughs or retorts, means for admitting forced draught air into) the fuel through said. tuyeres as it rises from the retorts and spreads over the tops of the tuyeres, extension grates at the rear ends of the retorts on which the final stage o f coin-- bustion is con'ipl'eted, longitudinal grate bars located parallel to the retorts, means for introducing a supplementary supply of air into. the partly burnt fuel through said lougitudinal grate bars so that an intermediate stage is introduced into the combustion process and means for cont-rolling the pressure of the air supplied through said longitudinal grate bars.

2. An uncl'er feed mechanical stoker coinn'ising troughs or retorts, means for feeding fuel into said troizighs or retorts, tuyeres at the sides of said troughs 01' retorts, means for admitting forced draught air into the fuel. through said. tuyeres as it rises from the retorts and spreads over the tops of the tuyeres, extension grates at the rear ends of the retorts on which. the final stage of combustion is completed, longitudinal grate bars localxjul parallel to the retorts, means for torts, means for admitting forced. draught air into the fuel through said. tuyeres, as it rises from the retorts and spreads over the tops of thetuyeres, extension grates at the rear ends of the retorts on which the final. stage of combustion is completed, longitudinal box shaped and stepped grate bars located parallel to, the retorts, meansfor introducing a supplementary supply of air under control into the partly burnt fuel throi'lgh said longitudinal grate bars so that an intermediate stage is introduced into the combustion process, and means for reciproeating said longitudinal grate bars so as to slice the thinner portions of the fuel bed as and when desired.

4. An underfeed mechanical stoker comprising troughs or retorl's, means for feeding fuel into said troughs or retorts, tuyeres at the sides of said troughs or re torts for the admission of forced draught air into the fuel as it rises from the retorts and s nreads over the tops of the tuyeres, extension grates at the rear ends of the retorts on which the final stage of combustion is completed, longitudinal box-shaped and stepped grate bars located parallel to the retorts, means for introducing a supplementary supply of air into the partly burnt i'uel through said longitudinal grate bars so that an intermediate stage is hit-reduced into the conil austion process and through said extension grates for final combustion of the fuel thereon, means for controlling the pressure of the air supplied through said longitudinal. grate bars and through said extension grates, and means for reciprocating said extension grates.

An underfeed mechanical stoker compi ng fixed troughs or retorts, means for feeding fuel into said trou hs or retorts d i i i b J fixed tuyeres at the sides of said troughs or retorts, for the admission of forced draught air into the fuel as it rises from the retorts and spreads over the tops of the tuyeres, extension grates at the rear ends of the retorts on which the final stage of combustion is completed, longitudinal grate bars located parallel to the retorts, means for inl'roducing a su1 plementary supply of air into the partly burnt fuel through said longitudinal grate bars so that an inter mediate stage is introduced into the combustion process and through said extension grates for final combustion of the fuel thereon, means for reciprocating said longitudinal orerfeed grate bars so as to slice the thinner portions of the fuel bed as and. when desired, and means for reciprocating said extension grates.

6. An underfeed meclnuiical stoker comprising troughs or retorts, means for feeding fuel into said trougl'is or retorts, tuyeres at the sides of said troughs or retorts for the admission of fm-cml draught air into the fuel it rises from the retorts and SIHUi-H'lfi over the tops of the tuyeres, fuel feeding pushers within said. troughs or retorts, extension grates at the rear ends of the retorts on which the final stage of comhustion is coin grlcted, longitudinal orerfecd grate bars located parallel. to the retorts, means for introducing a supplementary supply of air into the partly burnt fuel through said longitudinal overfeed grate bars so that an intermediate stage is introduced into the combustion process and through said extension grates for final combustion of the fuel thereon, means for reciprocating said longitudinal overfeed grate bars so as to slice the thinner portions of the fuel bed as and when desired, and means for reciprocating said transverse extension grates.

7. An underfeed mechanical stoker comprising troughs or retorts, means for feeding fuel into said troughs or retorts, tuyeres at the sides of said troughs or retorts for the admission of forced draught air into the fuel as it rises from the retorts and spreads over the tops of the tuyeres, extension grates at the rear ends of the retorts on which the final stage of combustion is completed, longitudinal 'rate bars located parallel to the retorts, means for introducing a supplementary supply of air into the partly burnt fuel through said longitudinal grate bars so that an intermediate stage is introduced into the combustion process, and through said ex-- tension grates for final combustion of the fuel thereon, means for imparting variable stroke reciprocating motions to said longitudinal overfeed grate bars, and means for imparting variable stroke reciprocating motions to said. extension grates whereby a slicing action may be imparted as desired to the thin parts of the fuel bed between arjaccnt units of the stokers. and to the fuel bed. over the extension grates.

8. An underfeed mechanical stoker co1nprising troughs or retorts, means for feeding fuel into said trougl'is or retorts, tuyeres at the sides of said troughs or retorts for the admission of forced draught air into the fuel as it rises from the retorts and spreads over the tops of the tuyeres, extension grates at the rearends of the retorts on which the final stages of combustion are completed, longitudinal grate bars located. parallel to the retorts, means for introducing a supple mentary supply of air into the partly burnt fuel. through said longitudinal grate bars so that an intermediate stage is introduced into the combustion process, and through said extension grates for final combustion of the fuel thereon, fuel feeding pusher-s located within said retorts, means for imparting-. variable stroke reciprocating motions to said pushers, means for imparting variable stroke reciprocating motions to said longitudimi-l overfeed grate bars and means for in'iparting variable stroke reciprocati n motions to said. extension grates, whereby a slicing action may be inmarted as desirml to the parts of the fuel bed between adjacent units of the stokers, to the thick parts of the fuel bed over the centre of the retorts, and to the fuel bed over the extension grates,

9. An underfeed mechanical stoker comprising troughs or retorts, means for feeding fuel into said. troughs or retorts, t-uyeres at the sides of said troughs or retorts for the admission of forced draught air into the fuel as it rises from the retorts and spreads over the tops of the tuyeres, extension grates at the rear ends of the retorts on which the final stage of combustion is completed, longitudinal box shaped and stepped grate bars located parallel to the retorts, means for introducing a supplementary supply of air under control and at low pressure into the partly burnt fuel through said longitudinal grate bars so that an intermediate stage is introduced into the combustion process, and through said extension grates for final combustion of the fuel thereon, fuel feeding pushers located within said retorts, means for imparting variable stroke reciprocating motions to said pushers, means for imparting variable stroke reciprocating motions to said longitudinal grate bars and means for imparting variable stroke reciprocating motions to said extension grates, whereby a slicing action may be imparted as desired to the parts of the fuel bed between adjacent units of the stokers, to the thick parts of the fuel bed over the centre of the retorts, and to the fuel bed over the extension grates.

10. An underfeed mecl'lanical stoker (our prising underfeed longitudinal retorts, tuyeres at the sides of said retorts for the admission of full pressure air, extension grates on which the final stage of combus tion is effected, longitudinal over-feed grates located parallel to the retorts, a low rn'cssure air chamber, and means for controlling the admission of air to said air chamber so as to distribute low pressure air from said air chamber to said extension grates and to said overfeed grates respectivel y CHARLES ERITH, 

